//1.类型注解
var name: string = "why"
let age: number = 18
const height: number = 1.88

//string与String的区别
//string:  Ts的字符串类型   所以类型注解用string
//String: js的字符串包装类的类型

const message: string = "hello ts"

//  变量类型推断
//  不添加类型注解
let foo = "foo"
// foo = 123






export {}